U.S. Pat. No. 3,333,789 discloses a technique for controlling missile dynamics depending upon whether a predetermined error threshold has been exceeded. It is not a technique for activating the tracking mode of a missile as in the present invention.
U.S. Pat. No. 3,798,420 is a technique for calculating angular velocities to enable the automatic tracking of a motor driven device, such as a gun sight, onto a moving target. It is not a circuit for transitioning between the non-tracking mode and the tracking mode of a missile as in the present invention. Rather, this patent operates solely within the tracking mode; it provides calculations used for a transition between manual tracking and automatic tracking.
This invention finds its applicability in guided missiles adapted to track a target, wherein the missile system includes means, which may be situated on board the missile or on board the object (e.g., airplane) launching the missile, for determining whether the target is or is not of sufficient "quality" to enable the missile's on-board tracking means to satisfactorily track the target. The "quality" measured may be the amplitude of an electromagnetic signal emanating or reflecting from the target combined with noise associated with the target's background. In prior art systems, this target quality measuring means produces some indication, such as an audible tone in the headset of the operator responsible for launching the missile, when adequate tracking quality has been achieved. In response to this signal, the operator manually activates a switch to place the missile into the tracking mode. The problem with this approach is that the operator's reaction time becomes a factor in target acquisition, and furthermore, especially in the case where the operator is a pilot flying solo in an aircraft, such manual activation is potentially dangerous because the pilot may be engaged in urgent maneuvers to avoid enemy fire, demanding his full attention. What is needed, therefore, is an automatic system for activating the tracking mode of the missile, wherein the system compensates for noise-induced jitter, has memory, and prevents reversion to the non-tracking mode at inopportune moments. These goals are accomplished by activation circuit 1 of the present invention.